Water-Quality Trends for Streams and Reservoirs in the Research Triangle Area of North Carolina, 1983-95
Sample Collection and Analysis Methods
USGS stream samples were collected with a depth-integrating sampler from a bridge or while wading. Multiple samples from the stream cross-section were composited by using a polycarbonate churn splitter and were processed and preserved on site (Garrett and others, 1994). DWQ stream samples were grab samples collected at the center of flow. USGS and DWQ lake samples were collected from a boat by using an interval sampler. Except as noted below, nutrient and chlorophyll a samples were integrated within the photic zone (twice the secchi depth), whereas major ion and trace-element samples were collected at 0.5 foot (ft) below the water surface. From April 1989 through March 1992, USGS chlorophyll a and nutrient samples were collected at 0.5 ft below the water surface at University Lake, Cane Creek Reservoir, Lake Michie, Little River Reservoir, and Lake Benson (beginning in 1990).
USGS samples collected for analysis of nutrients, chlorophyll a, major ions, and trace elements were filtered (if required), packed on ice, and shipped to the USGS National Water Quality Laboratory in Arvada, Colo., for analysis. Results were stored in the USGS National Water Information System data base. DWQ samples collected for analysis of nutrients and selected metals were analyzed by the DWQ laboratory in Raleigh, N.C. Results were stored in the USEPA Storage and Retrieval (STORET) data base. The USGS sample-collection and analysis methods used for this project are detailed by Garrett and others (1994).
Lake samples being prepared for laboratory analysis.
Last modified: Wed Jun 10 10:40:39 1998
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